Where does multicast show up in real ops work, and why does it break the moment you move to the cloud?

VRRP heartbeats, market data feeds, mDNS noise and cluster chatter all ride multicast, and all of it assumes a switched LAN. Why clouds drop it and what replaces it.

Grounded in researched DevOps, SRE and platform engineering interview loops, written to a senior-engineer editorial bar, and never padded to hit a word count.